The United States is the world's fourth largest country, with an area of 3,679,192 square miles (9,529,107 square kilometers). It includes fifty states and one federal district, where the capital, Washington, D.C., is located. The environment is extremely diverse and often spectacular. Alaska's glaciers coexist with flowering tundra that bloom in the arctic summer. Niagara Falls, Yellowstone National Park, and the Grand Canyon are a few well known landscapes.